New color to brush converter

New boolean to visibility converter
Base class to handle property changes notifications for all View Models
Template selector to handle a different first item in listviews or gridviews

ModernKeePass/Converters/PluralizationConverter.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Collections.Generic;
 using Windows.UI.Xaml.Data;
 
 namespace ModernKeePass.Converters